The present invention relates to a device for inserting, extracting and locking a module into, from and in a rack, this module having to be connected to one or more connection elements when it is inserted into the rack. Connection may, in particular, be of the electrical type, and it is possible to envision for the connection to be of one or more other types, for example optical, mechanical, pneumatic, thermal, etc.
The description which will be given will apply to an electrical connection, but it could just as easily relate to a connection of some other type.
A module bearing one or more printed circuit boards is intended to fit into a rack in the manner of a drawer. The module has connection elements which plug together with other connection elements secured to the rack.
During insertion, the insertion, extraction and locking device has to overcome forces that are due to the connection elements. It has also to keep to a sequence of steps preceding connection proper, such as the pre-guiding of the module into the rack and decoding of the module to be sure that the module fitted is the right one and that its orientation is correct.
When the module is fully fitted into the rack, its printed circuit boards are connected to an electrical installation via the connection elements and the insertion, extraction and locking device, in its locked position, has to prevent accidental disconnection and provide a good connection even under severe conditions of use, for example in the face of significant vibrations, knocks, sharp accelerations, in a damp and/or saline environment, etc.
During extraction, the insertion, extraction and locking device has to allow the forces of unplugging the connection elements to be overcome.
The installations concerned may be, but are not exclusively, located on board heavier-than-air craft. In this application in particular, the safety of the connections is of prime importance; momentary breaks in the electrical or other connections may be particularly troublesome and dangerous in the case of real-time working, during data acquisition procedures or controlling parts of the heavier-than-air craft, etc.
There is an aim, particularly in integrated modular avionics systems, for the maintenance of such modules to be simple and effective. The modules have to be able to be installed quickly and their connection has to be extremely secure.
Quick disconnection and release of the modules has also to be possible, for repair or exchanges purposes.
An insertion, extraction and locking device is known, for example, from patent application FR 2 742 588. This comprises, secured to the module, a lever which can move in terms of rotation with, at one of its ends, a hook intended to catch on an anchoring pin connected to the rack, generally to its base, and secured to a spring. Being fixed to the rack at one end and to the anchoring pin at the other end, the spring exerts a return force directed toward the inside of the rack when the hook is caught on the anchoring pin. The other end of the lever comprises means for attaching the lever to the module. In the locked position, a remanent force is exerted on the connections as a result of the spring.
A device such as this is not entirely satisfactory. This is because in environmental conditions including strong vibrations, accidental disconnections may arise.
The insertion, extraction and locking device secures the module into the rack only by the hook at the base of the rack.
In the event of vibration, the module can oscillate in the rack. The rack generally comprises two slideways facing each other, one at the top and the other at its base, and the module is slid along these slideways. However, there is a certain amount of clearance provided between the module and the slideways in order to take account of tolerances on the module and those on the rack. Connections located at the back of the rack, on a diagonal with respect to the anchoring point, may therefore be disturbed if the module vibrates and begins to rock.
Another drawback of this insertion, extraction and locking device is associated with the size of the parts of the device supported by the base of the rack. The rack bears the spring and the hook anchoring pin. Space has to be made to house these parts and this space encroaches on the volume for storing the modules. The printed circuit boards housed in the modules have a smaller surface area than boards placed in modules associated with insertion and extraction devices in the form of simple levers but which do not fulfil the function of permanently maintaining the load.
It has also been found that this insertion, extraction and locking device cannot guarantee correct and complete connection of the module upon each insertion. If there is abnormal or excessive resistance in the connector blocks or if any obstacle arises during insertion, the return spring may completely compress and the lever may be locked without the module being completely and reliably fitted into the rack. There is a risk that the connections will be strained or damaged without the operator who has just performed this incorrect operation noticing.
The object of the present invention is to offer a particularly reliable insertion, extraction and locking device which guarantees undisrupted connection when operating in a harsh environment.
Another object of the present invention is to offer an insertion, extraction and locking device which prevents any incorrect or incomplete connection of the module.
Another object of the present invention is to offer an insertion, extraction and locking device which is compatible with standard modules and existing racks.
In order to achieve this, the present invention is a device for inserting, extracting and locking a module into, from and in a rack, comprising:
two arms which can pivot with respect to the module and which are articulated together by a common articulation, each of them comprising, on the one hand, at one end, means of anchoring it into the rack and, on the other hand, a non-common articulation with the module,
means capable of immobilizing one of the arms with respect to the other when both of the arms are anchored in the rack, and
associated with at least one of the arms, elastic means working in compression between the module and the said arm when its end is anchored into the rack.
The elastic means may comprise one or more elements such as springs or Belleville washers.
When use is made of Belleville washers, these may form one or more packets, each comprising one or more first Belleville washers mounted a first way round, and one or more second Belleville washers mounted a second way round, the first way round being the opposite of the second, so as to obtain a stiffness which is perfectly tailored to the module and to the forces it experiences.
According to a first configuration of the insertion, extraction and locking device, the non-common articulation specific to one arm may comprise a clevis secured to the module, this clevis having two branches which support a pivot passing through a slot in the arm.
According to another configuration, the non-common articulation specific to one arm may comprise a pivot which projects from the module through a slot in the said arm, the arm being held on the pivot by a pin which can be prevented from translational movement.
A certain amount of clearance is preferable at a non-common articulation so as to make the insertion, extraction and locking device easier to manipulate.
The elastic means may be located at a non-common articulation or more simply may be offset therefrom.
The anchoring means may be a two-pronged fork, these prongs straddling a boss borne by the rack upon anchoring.
To assist with the insertion and extraction of the module, it is preferable for the prongs to have different lengths, the shorter prong being received between the boss and the module.
The common articulation may be of the hinge type. To make the insertion, extraction and locking device easier to manipulate, it is preferable for it to leave a clearance between the two arms.
The means capable of immobilizing one of the arms with respect to the other may comprise a notch borne by one of the arms and a hook integral with the other arm, the hook being inserted in the notch.
To avoid accidental disengagement of these immobilizing means, provision may be made for the hook to be kept inserted in the notch by elastic means.